1. Field of the Invention
The present invention relates to a solid-state imaging apparatus.
2. Description of the Related Art
Solid-state imaging apparatuses that are mounted in digital still cameras, video cameras, and cellular phones are being actively developed in recent years. CCD (Charge Coupled Devices) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors are widely known as solid-state imaging apparatuses. In particular, increasing levels of attention are being focused on CMOS sensors whose features include, in comparison to CCD sensors, lower power consumption, capability of high speed readouts, and system-on-a-chip integration.
A CMOS sensor includes an amplifier circuit that includes a floating diffusion amplifier or the like for each pixel. When reading out pixel signals, a method is widely used that selects a certain row from a pixel array portion in which a plurality of pixels are arranged in a matrix in a row direction and a column direction, and simultaneously reads out the pixel signals of all the pixels located in the selected row.
Demands for improving solid-state imaging apparatuses to achieve higher pixel densities and higher operation speeds are continuing to increase. For example, Japanese Patent Application Laid-Open No. 2005-311821 (hereafter, referred to as “Patent Document 1”) discloses an apparatus that realizes a high speed readout by arranging a plurality of vertical output lines in each row and reading out a plurality of rows simultaneously.
However, according to the solid-state imaging apparatus described in Patent Document 1, although the apparatus is improved into a high operation speed by arranging a plurality of vertical output lines in each row and reading out pixel signals of a plurality of rows simultaneously, the area ratio of a photoelectric conversion element decreases because a buffer is provided for each pixel. That is, it is difficult to improve the solid-state imaging apparatus to achieve a high pixel density so that each pixel obtains a predetermined aperture ratio.
The present invention has been made in view of the above described problems, and an object of the invention is to provide a solid-state imaging apparatus that shortens a time for reading out pixel signals of all pixels, and improves the aperture ratio of pixels.